Various dental materials having dental materials are known in the art. For example, U.S. Pat. No. 6,730,156 describes a filler comprising a substantially amorphous cluster comprising non-heavy metal oxide particles and heavy metal oxide. The filler can be mixed into a hardenable resin to provide radiopaque dental materials having desirable strength and aesthetic character.
U.S. Pat. No. 6,572,693 describes a material having a hardenable resin; and a filler comprising (i) clusters of nano-sized particles, the clusters comprising non-beavy metal oxide particles and heavy metal oxides, and being not fully densified particles and (ii) non-agglomerated nano-sized particles selected from the group consisting of non-heavy metal oxide particles, heavy metal oxide particles, and combinations thereof. The material is suitable for use as dental materials.
U.S. Pat. No. 7,981,513 describes a dental filler having the optical and/or mechanical properties satisfying the requirements to a dental material, a method for producing the dental filler, and a dental composite material containing the dental filler. The dental filler comprises microparticles of amorphous inorganic oxide constituted by at least silica-based fine particles covered with a composite oxide comprising zirconium, silicon and oxygen. The dental composite material contains the dental filler and a hardenable resin selected from an acrylic resin, a methacrylic resin, an epoxy resin, a vinyl resin and a urethane resin.